The present invention relates generally to the transportation of items on a railroad and, more particularly, to fixtures used to transport wind turbine blades on railcars for travel on the railroad and methods of supporting the wind turbine blades during such transport.
Wind farms employing large numbers of wind turbines to generate electricity have become increasingly popular alternative energy sources. The wind turbine blades, towers, hubs, nacelles and other components are normally transported separately by cargo ship, truck, and/or railcar from their manufacturing sites to the wind farms where they are assembled to form the operational wind turbines.
As wind turbines continue to grow in height and blade length, challenges have arisen in transporting the wind turbine blades by railcar. When a wind turbine blade is transported by railcar, a root end fixture and a mid-frame fixture are normally mounted on the deck of the railcar and are used to support the root end and a reinforced midsection of the wind turbine blade, respectively. When the wind turbine blade has a length that is less than the length of a single railcar, the root end fixture and the mid-frame fixture are mounted on the same railcar. A longer wind turbine blade up to a certain length may still be supported by the root end and mid frame fixtures that are located on the same railcar, with the tip end of the wind turbine blade extending over an adjacent railcar. In this arrangement, the railcar on which the root end and mid-frame fixtures are mounted is commonly referred to as the load car, and the adjacent railcar over which the tip end extends is commonly referred to as the idler car. For wind turbine blades of even greater length, the mid-frame fixture must be located on the adjacent railcar from the root end fixture and both of the railcars operate as load cars. Placement of the root end and mid-frame fixtures on separate railcars is problematic because one or both of the fixtures must be permitted to move about one or more pivot axes to accommodate the relative movement between the adjacent railcars as they navigate curved sections of the railroad.
The longer wind turbine blades create additional problems because their tip ends must be restrained from swinging outwardly beyond a specified distance from the railcar as the railcars travel around curved sections of the railroad. Keeping the tip ends within the specified clearance window is particularly problematic with blade configurations having a curved profile that is designed to prevent the tip end of the blade from contacting the support tower of the operating wind turbine when wind loads cause flexure of the rotating blades. Tip end fixtures have been developed to retain the tip end of the wind turbine blade within the specified clearance window during railcar transport, but the challenge of restraining the wind turbine blade without causing damage to it has become more difficult as the wind turbine blades continue to increase in length and have adopted the curved profile.
A need has thus developed for improved fixtures for supporting wind turbine blades during railcar transport.